Manage your subscription

Herpes gene tackles brain tumours

By SUBHADRA MENON

A PIONEERING form of gene therapy for brain tumours has shown remarkable
promise in a trial with 15 patients. Some tumours had shrunk noticeably within
two weeks, and one patient who was not expected to live for more than 6 months
survived for 25 months.

At the XVI International Cancer Congress in Delhi last week, Michael
Blaese, head of the Clinical Gene Therapy Branch at the US National Institutes
of Health in Bethesda, Maryland, described the preliminary findings of the
trial. The results are “so promising”, he said, that the team will move on to
a larger trial.

Blaese stressed that it is still too early to get excited. “I do not want
to mislead people by saying this is the magic bullet that is going to cure
brain cancer, but I do hope this will be another tool that will be effective
in cancer treatment.”

The gene therapy is designed to destroy tumour cells while leaving healthy
brain cells untouched. The brain tumour is injected with a mouse retrovirus
that has been engineered to carry a gene from the herpes simplex virus, which
infects only dividing cells. Tumour cells divide rapidly, but healthy brain
cells do not divide at all.

The herpes gene instructs the cell to produce the enzyme thymidine kinase,
which makes the cell susceptible to the antiherpes drug ganciclovir. After
treatment with the virus, patients are given ganciclovir, which destroys cells
that produce thymidine kinase.